The subject is an improvement over the device shown and claimed in U.S. Pat. No. 3,673,463 which issued on Jun. 27, 1972 to M. C. Gourdine, which patent is incorporated herein by reference.
In the electrogasdynamic apparatus described in said patent, certain shortcomings have been noted with respect to accumulation or contamination of the powdered coating at the point of the electrode, as well as within the non-conducting flow channel in which the ionized particles are propelled by air pressure toward the object to be coated. More particularly, it has been found that contamination (the buildup of powdered coating material) is particularly noticeable at the collector ring, and at the electrode needle, and after a period of time of buildup, the efficiency of the electrogasdynamic apparatus is markedly decreased. Furthermore, through experimentation it has been found that the electrical charge on the particles is continually degraded with operation of the electrogasdynamic apparatus, and after relatively short periods of time, it is necessary to shut down the apparatus, and clean the entire electrogasdynamic gun assembly. As is apparent, with the constant degradation of the space charge on the particles the efficiency of the coating process is markedly decreased, and this thereby results in decreased powder output, increased cost of production, increase maintenance costs, and overall inefficient operation of the apparatus.
Accordingly, it is the object of the subject invention to overcome the shortcomings of the prior art devices, and provide a new and improved electrogasdynamic gun apparatus which achieves minimum contamination at the collector ring and at the electrode needle; requires less current to operate; operates over continuously long periods of time; provides a constant or uniform non-varying space charge to the particles; provides more efficient powder coating of the objects to be coated; increases the amount of powder material output; is cheaper to operate, requiring less maintenance and downtime; and furthermore because of the new and improved characteristics of the subject electrogasdynamic gun apparatus is capable of applying coating materials such as porcelain frit which heretofore has not been able to be applied through the use of conventional electrogasdynamic coating apparatus.